THE ALKALINE CUPRIC OXIDE OXIDATION OF HUMIC AND FULVIC ACIDS EXTRACTED FROM TROPICAL VOLCANIC SOILS

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Abstract
Certain infertile tropical volcanic soils in the West Indies tend to accumulate unusually large amounts of organic matter. To obtain a better understanding of the exceptional behavior of this type of organic matter, and in order to eventually devise remedial action, we degraded by alkaline cupric oxide oxidation six humic acids and six fulvic acids extracted from problem soils on the island of Dominica. The oxidation products were fractionated by solvent extraction and chromatographic methods and 46 compounds were identified on a gas chromatography-mass spectrometry-computer system. Major oxidation products (identified as esters and ethers), as percentages of total compounds identified, were: n-fatty acids (13.1–22.2 percent for humic acids, 14.6–33.1 percent for fulvic acids), phenolic acids and aldehydes (52.1–62.4 percent for humic acids, 18.5–41.0 percent for fulvic acids), and benzene-carboxylic acids (18.5–25.7 percent for humic acids, 17.0–38.1 percent for fulvic acids). The major n-fatty acids were palmitic and stearic acids. Most of the fatty acids appeared to be esterified to phenolic compounds. Our data show that the chemical structure of the humic and fulvic acids extracted from the tropical volcanic soils does not appear to differ significantly from that of humic and fulvic acids extracted from soils formed under widely differing geographical and pedological environments.

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